Many interesting and perplexing questions arise in connection with the highly potassic volcanic associa tion dominated by mafic and ultramafic rocks contain ing leucite. Its occurrence is very restricted as compar ed with the olivine-basalt trachyte kindred, but it is distributed at widely scattered points on all the conti nents, and its chemical and petrographic individuality is both remarkable and constant. A considerable litera ture is available related to the mineralogy, petrology, geochemistry, phase chemistry, distribution, and origin of this interesting suite of rocks. It seemed that there was a genuine need for a review-synthesis of all these data, which would be intelligible to a wide spectrum of advanced students and professionals in the earth sciences. The monograph may be divided into two parts. The first part consists of six chapters in which the mineralogical and chemical peculiarities of leucite bearing rocks and their nomenclature, petrology, min eralogy, distribution, and physical and chemical condi tions of formation are discussed. Phase equilibria stud ies on many leucite-bearing ternary, pseudoternary, quaternary, and pseudoquaternary joins and systems, studied by different investigators at variable tempera tures in air, are described in the second part in Chap ters 7 to 12. Survival of leucite and formation of pseu doleucite is discussed in Chapter 13. Leucite-bearing synthetic and natural rock systems studied at different temperatures under variable pressures in presence or absence of water, are summarized in Chapters 14 and 15. 1 Introduction.- 1.1 Basalt and its Relation to Leucite-Bearing Mafic and Ultramafic Rocks.- 1.2 Mineralogical Composition and Other Geochemical Peculiarities of Leucite-Bearing Rocks.- 1.3 A Brief Summary of the Hypotheses of Origin of Leucite-Bearing Rocks.- 1.4 Objective of This Study.- 2 Nomenclature and Petrography of Leucite-Bearing Rocks.- 2.1 Nomenclature.- 2.1.1 Italite.- 2.1.2 Leucitite.- 2.1.3 Olivine Leucitite.- 2.1.4 Melilite Leucitite.- 2.1.5 Katungite.- 2.1.6 Leucite Tephrite.- 2.1.7 Leucite Basanite.- 2.1.8 Melilite-Nepheline Leucitite.- 2.1.9 Jumillite.- 2.1.10 Verite.- 2.1.11 Wolgidite.- 2.1.12 Fitzroyite.- 2.1.13 Mamilite.- 2.1.14 Cedricite.- 2.1.15 Wyomingite.- 2.1.16 Orendite.- 2.1.17 Madupite.- 2.1.18 Potassium-Rich Ankaratrite.- 2.1.19 Mafurite.- 2.1.20 Shonkinite.- 2.1.21 Absarokite, Banakite, and Shoshonite.- 3 Mineralogical Composition of Leucite-Bearing Rocks.- 3.1 Leucite.- 3.2 Nepheline.- 3.3 Kalsilite.- 3.4 Kaliophilite.- 3.5 Sanidine.- 3.6 Plagioclase.- 3.7 Pyroxene.- 3.8 Olivine.- 3.9 Mica.- 3.10 Potash Richterite.- 3.11 Melilite.- 3.12 Analcite.- 3.13 Accessory Minerals.- 3.13.1 Sodalite.- 3.13.2 Apatite.- 3.13.3 Priderite.- 3.13.4 Wadeite.- 3.13.5 Other Minerals.- 4 Minor and Trace Element Geochemistry, Initial 87Sr/86Sr Ratios and Oxygen Isotopic Ratios of Leucite-Bearing Rocks.- 4.1 Trace Element Geochemistry.- 4.2 The Initial 87Sr/S6Sr Ratios of Highly Potassic Lavas and Other Rock Types.- 4.3 ? 18O-contents of Leucite-Bearing Rocks.- 5 Distribution of Leucite-Bearing Rocks.- 5.1 Volcanic Fields, East and Southeast of Ruwenzori, Uganda.- 5.2 Birunga Volcanic Province.- 5.3 Leucite-Bearing Rocks of West Kimberley, Australia.- 5.4 Leucite-Bearing Rocks of New South Wales, Australia.- 5.5 Leucite-Bearing Rocks of Indonesia.- 5.6Volcanic Fields of Highwood Mountains, Montana (USA).- 5.7 Potassic Rocks of Navajo-Hopi Province (USA).- 5.8 Leucite-Bearing Rocks of Leucite Hills, Wyoming (USA).- 5.9 Leucite-Bearing Rocks of Italy.- 5.9.1 Monti Vulsini.- 5.9.2 Vico Volcanic Complex.- 5.9.3 Monti Sabatini.- 5.9.4 Colli Albani (Alban Hills).- 5.9.5 Phlegrean Fields.- 5.9.6 Somma-Vesuvius.- 5.9.7 Roccamonfina.- 5.9.8 Volcanic Activity in the Eolian Arc Region.- 5.10 Volcanic Provinces of Spain.- 5.11 Leucite-Bearing Lamprophyres of Eastern India.- 5.12 Leucite-Bearing Rocks of the Laacher See and Other Areas of West Germany.- 5.13 Leucite-Bearing Rocks of the Tristan da Cunha Islands.- 5.14 Leucite-Bearing Rocks of Manchuria, China.- 5.14.1 Wu-ta-lien-chih.- 5.14.2 Erh-Ko.- 5.14.3 Chi-hsing Shan.- 5.15 Leucite Bearing Rocks of Utsuryo Island (Ullung-do), Korea.- 6 Conditions of Formation of Leucite-Bearing Mafic and Ultramafic Rocks.- 6.1 Chemical Conditions.- 6.2 Silica Activity in Leucite-Bearing Rocks.- 6.3 Physical Conditions.- 7 Leucite-Bearing Ternary Joins and Systems.- 7.1 The System Nepheline-KalsiliteSiO2.- 7.2 The System Diopside-Leucite-SiO2.- 7.3 The System Anorthite-Leucite-SiO2.- 7.4 The System Diopside-Sanidine-Albite.- 7.5 The System Diopside-Nepheline-Sanidine.- 7.6 The System Nepheline-Leucite-Anorthite.- 8 Leucite-Albite Incompatibility.- 8.1 The Join Leucite-Albite.- 8.1.1 Composition of Alkali Feldspars in the Leucite-Albite-Join.- 8.2 The Join Leucite-Albite-Anorthite.- 8.2.1 Compositions of Ternary Feldspars in the Leucite-Albite-Anorthite Join.- 8.3 Petrological Implications.- 9 Leucite- and Feldspar-Bearing Quaternary Joins and Systems.- 9.1 The System Forsterite-Diopside-Leucite-Anorthite.- 9.1.1 The Join Forsterite-Diopside-Anorthite.- 9.1.2 The Join Forsterite-Anorthite-Leucite.- 9.1.3 The Join Diopside-Leucite-Anorthite.- 9.1.4 Paragenesis.- 9.2 The System Diopside-Leucite-Anorthite-SiO2.- 10 The System Forsterite-Diopside-Akermanite-Leucite.- 10.1 The Join Diopside-Akermanite-Leucite.- 10.2 The Join Forsterite-Diopside-Leucite.- 10.3 The Join Forsterite-Akermanite-Leucite.- 10.4 The Join Forstente-Diopside-Akermanite.- 10.5 The Join Diopside-Akermanite-Leucite with 3% For
